The present disclosure relates to a common mode filter.
In accordance with the advancement of technology, electronic devices such as mobile phones, home appliances, personal computers (PCs), personal digital assistants (PDAs), liquid crystal display (LCDs), and the like, have been changed from an analog scheme to a digital scheme, and the speed of electronic devices has increased due to an increase in an amount of processed data. Therefore, a universal serial bus (USB) 2.0, a USB 3.0, and a high-definition multimedia interface (HDMI) have widely spread as high-speed signal transmitting interfaces, and have been used in many digital devices such as personal computers and digital high-definition televisions.
These high speed interfaces adopt a differential signal system which transmits differential signals (differential mode signals) using a pair of signal lines, unlike a single-end transmitting system that has generally been used for a long period of time. However, electronic devices that are digitized and have increased speeds are sensitive to external stimuli, and thus signal distortion due to high frequency noise is often generated.
Causes of this abnormal voltage and noise include switching voltage generated in a circuit, power noise included in a power supply voltage, an unnecessary electromagnetic signal or electromagnetic noise, and the like, and a common mode filter (CMF) has been used as a unit for preventing the above-mentioned abnormal voltage and high frequency noise from being introduced into a circuit.
A common mode filter according to the related art may mainly be divided into a multilayer common mode filter and a thin film type common mode filter.
In a case of the multilayer common mode filter, coil layers are formed on ceramic sheets, and the ceramic sheets on which the coil layers are formed are stacked, compressed, and sintered, and thus close adhesion between the coil layers may be secured. However, in the multilayer common mode filter, since a conductive paste is used in a process of forming the coils, precision of a coil pattern is low, and resistance of the coil pattern is high.
In a case of the thin film type common mode filter, since respective layers are formed using a method such as coating, or the like, after a polymer resin is hardened, close adhesion between the layers is low. A method of enhancing bonding through a silane coating has been used in order to increase close adhesion of the thin film described above. However, close adhesion, or the like, is lower in the thin film type common mode filter than in the multilayer common mode filter. Therefore, a method that may increase the close adhesion has been required.
In addition, in the thin film type common mode filter, in a case of forming the common mode filter by bonding a magnetic layer to a ferrite substrate on which the coil is formed, an entire thickness of the common mode filter is reduced, and thus a handling problem occurs in a process of manufacturing the common mode filter, whereby yield is reduced due to defects such as generation of cracks, or the like, when the thickness of the common mode filter is reduced.
Therefore, a common mode filter that may satisfy low costs and superior electrical features, and a method of manufacturing the same, has been required.